Comments on Ekino et al. Cloning and Characterization of a Unique Cytotoxic Protein Parasporin-5 Produced by Bacillus thuringiensis A1100 Strain.

LEOPOLDO PALMA

Toxins

MDPI

Lugar: Basel; Año: 2015 vol. 7 p. 5094 - 5095

2072-6651

Ekino and collaborators reported the cloning and characterization of the cytotoxic protein Parasporin-5 produced by Bacillus thuringiensis A1100 Strain. The 33.8-kDa inactive precursor protein exhibited cytocidal activity upon proteinase K activation against MOLT-4 cells and showed slight homology against Cry and aerolysin-type β-pore-forming toxins. Despite in this work, the authors demonstrated the potential toxic activity of this protein against MOLT-4 cells, further studies should have been performed in order to ensure the absence of insecticidal activity of the B. thuringiensis strain, since at least in this work, there are no mention about any bioassay performed against insects with this strain or protein. Palma and collaborators reported the molecular and insecticidal caracterization of a novel Cry-related protein closely related to parasporins Cry41Aa1 and Cry41Ab1. This protein did not show any toxic activity against five species of lepidoptera. Such results, preliminarly suggested the potential parasporin activity of this Cry-related protein. However, its finally showed a specific toxic acitivity against the green-peach aphid Myzus persicae. Nowadays, parasporin proteins are defined in the literature, as non-insecticidal proteins produced by B. thuringiensis that exhibit significant and specific toxic activity against human-cancer cells of various origins. However, most of the research works about parasporins have been mainly perfomed in order to demonstrate their goodnesses as potential terapeutic agents against cancer while they are lacking research supporting the absence insecticidal activity. The complete absence of insecticidal activity needs to be more deeply investigated since the B. thuringiensis toxins have demonstarted throughout the last decades to be not only specifically active but also toxic against a wide range of insects. Therefore, the determination of the activity against a wider range or insects might change the non-insecticidal concept we currently have about this proteins class from B. thuringiensis.